The present invention is directed to a method for applying or forming profiles having a mushroom-shaped cross section as closure elements along two longitudinal edges of a plastic web that is heat-shrinkable transversely relative to the longitudinal direction.
The fastening of a soft, planar material can occur in a known way according to the method of a "garter belt". In this arrangement, a hard substrate is applied to one side of the material, wherein a soft, planar material is deformed so that it surrounds the hard substrate to such an extent that it cannot be removed in the motion direction mechanically stressing the soft, planar material without having the soft, planar material either distorted or destroyed. The removal is thereby prevented in that a comparatively non-deformable member having a concave inside contour is placed over the thickening produced and the contour of the soft, planar material by the substrate, so that the thickening has an undercut in a roughly mushroom shape that makes a removal of the thickening from the outer, concavely-shaped member impossible without destruction. In a garter belt, the inner, hard member is connected button-like to the outer, hard member with a band which is flexible, but captive fashion, whereas the outer, hard member comprises a known pear-shaped opening and is usually formed of a bent wire. The broader part of the opening, thus, allows the insertion of the button together with the hose material placed thereover to pass through, whereas the narrower part of the opening, in fact, surrounds the planar material shaped around the button-shaped member, but does not allow the button with its cladding of hose material to pass. Such a two-dimensional example only allows the closure to be opened in the opposite direction on the line-shaped assembly path and prevents disassembly in all other directions of motion.
When such a closure having a profile-shaped, inner member is executed in this way, then the closure means for shrink collars, particularly for reinforced shrink collars, can be manufactured so that they constitute a one-dimensional example of this principle. In such shrink collars, the principle that has been set forth is applied in such a fashion that a rod-shaped element is arranged along the longitudinal edges of the shrinkable web composed of plastic. After each longitudinal edge has been folded around the rod-shaped insert to form what is referred to as a mushroom head, the two longitudinal edges, which have been provided with the rod-shaped inserts, are then pressed against one another. What is referred to as a "mushroom head" here is the fact that the edges comprise a profile having a mushroom cross section. A C-shaped rail is then drawn on over these mushroom heads. In the manufacturing process, the edge of the collar material is placed to extend along the rod-shaped, hard member so that the flexible flat material in the region of the closure will have twice the thickness of the edge region occurring, and this comprises a thickened edge whose core is non-resilient. When the rail is then thrust over the thickening, this can no longer be a non-destructively released transversely relative to the push-on direction from the closure element having a mushroom-shaped section.
European Published Patent Application 0 272 364 discloses a method in accordance wherein an enclosure rod insert can occur. It may be derived therefrom that the enclosure of the rod insert is undertaken in a discontinuous process, for example only over a length corresponding to the collar. A longitudinal edge of the collar is respectively bent over loop-shaped therein, and is clamped in a clamp device in collar length and the rod is introduced into the loop contour. Subsequently, the loop is reshrunk onto the introduced rod by heating. A disadvantage of this is that the collar material provided with a shrinkable fabric must be heated to shrink temperature for reshaping in the edge regions in order to thereby make it soft and elastic. As a result of the shrinking, the material becomes thicker and the amount by which it becomes thicker depends on the loop geometry, which is not easy to reproduce, as well as on the initial thickness of the material that is, likewise, dependent on the local stretch factor, which is also not easy to reproduce, and also on the strength of the material before stretching. The geometry of the edge after shrinking has been finished is, thus, critically dependent on the shrink properties of the material. The shrink process itself is dependent on the material deformation that is dependent on the factors cited here, for example deformation produced by unknown forces and tensions, and it follows therefrom that the edge contour or edge geometry cannot be exactly predetermined. The edge geometry can only be tolerated to a limited degree for the application of the C-rail. After the softening of the matrix, moreover, the threads of the fabric insert that essentially effect the shrinking forces can easily pull out from the edge region, due to the longitudinal shrink inherent in them, or can change their position within the matrix. In addition, in this type of edge treatment, a part of the shrink dimension is used and is, thus, no longer available for the actual function of the collar. As a result of the shrinking process in the loop region, the loop region is thickened without the hard rod insert likewise correspondingly increasing in thickness, as a result whereof the difference between the expanse of the thickened region having the mushroom-shaped cross section and the part having the cross section shaped like a mushroom stem have twice the thickness of the collar material which is situated in the clamp mechanism during production, and this difference is usable for the closure of the collar and requires a less beneficial shaping of the C-rail.
U.S. Pat. No. 4,379,473, whose disclosure is incorporated herein by reference thereto and which claims priority from German Application 30 09 078, also discloses a longitudinally divided cable sleeve of shrinkable material having embedded reinforcing means and beads along the closure regions. These longitudinal beads provided with rod inserts are individually introduced therein into the longitudinally proceeding channels of the T-shaped closure rail and are held together.
A method for manufacturing sheet metal profiles from bands of material are also generally known from the sheet metal industry, wherein the profiling is undertaken step-by-step utilizing roller sets in a continuous process on the basis of the stations arranged following one another. Such a method, however, cannot be employed for the plastic material of which the shrink collars are manufactured, particularly when a collar material having the reinforcing insert is involved, because these collar materials do not have the plasticity of the sheet metals employed for the profile manufacture and the deformation is, therefore, undone to a certain extent following each stage. Moreover, the low internal strength of the collar material also simultaneously causes a proportion of longitudinal dilatation in the intentional deformation at the roller sets of the shaping device, and this longitudinal dilatation noticeably deteriorates the planarity of the collar and its applicability and making a comfortable slip-on of the C-rail impossible. The longitudinal dilatation also necessarily effects a lateral excursion of the web edges from the sets of rollers of the shaping means in the continuous deformation process.